Handheld computing device having drop-resistant LCD display

ABSTRACT

A display for a handheld computing device includes a display panel; a circuit board carrying display electronics for the display panel; a cover assembly securing the display panel to the circuit board; and a resilient layer adhered to the circuit board for securing the display to the computing device.

FIELD OF THE INVENTION

The invention described herein relates to a handheld computing device.In particular, the invention described herein relates to a configurationfor a handheld computing device having a LCD display that is resistantto shock loading damage due to impact.

BACKGROUND OF THE INVENTION

The conventional handheld computing device, such as a PDA, or a wirelesstelephone, includes a keyboard/keypad, a display assembly and a systemmotherboard (not shown) contained within a common housing. The displayassembly is typically provided as a reflective, transmissive ortransreflective LCD display panel.

To limit power losses and the effects of noise on image quality, the LCDdisplay electronics must be disposed in close proximity to the LCDdisplay panel. Accordingly, the LCD display electronics are provided ona printed circuit board that is housed within a plastic or metal supportframe, together with the LCD display panel. Typically, the displayelectronics and the LCD display panel are press-fitted within the frame,and the frame is secured to the motherboard with permanent adhesive orscrews.

The LCD display panel is prone to damage resulting from shock loadingdue to impact. Since the LCD display panel is fixed within the supportframe, and the support frame is secured to the motherboard, the LCDdisplay panel can sustain shock impact damage if the handheld computingdevice is struck or dropped.

Further, in view of the method by which the LCD display panel and theLCD display electronics are assembled together, typically the entiredisplay assembly must be discarded if the LCD display panel becomesdamaged. As a result, repairs cost are often excessively high.

Therefore, there is a need for a configuration for a handheld computingdevice that reduces the sensitivity of the LCD display panel to jarringimpact damage. Further, there is a need for a configuration for ahandheld computing device that reduces the repair costs of the displayassembly.

SUMMARY OF THE INVENTION

According to one aspect of the invention described herein, there isprovided a display for a handheld computing device that includes adisplay panel; a display circuit board carrying display electronics forthe display panel; a cover assembly securing the display panel to thedisplay circuit board; and a resilient layer adhered to the displaycircuit board for securing the display to the computing device.

According to another aspect of the invention described herein, there isprovided a handheld computing device that includes a system motherboard;and a display resiliently secured to the system motherboard The displaycomprises a display panel; a display circuit board carrying displayelectronics for the display panel; a cover assembly securing the displaypanel to the display circuit board; and a resilient layer adhered to thedisplay circuit board and the motherboard.

In one implementation, the display also includes a backlight, and alight guide frame disposed between the backlight and the display panel.The display circuit board is a rigid, flexible or semi-rigid circuitboard. The light guide frame includes at least one snap clip thatretains the display to the handheld computing device. The resilientlayer comprises a foam layer. The foam layer has a permanent adhesivesurface adhered to the display circuit board, and a removable adhesivesurface adhered to the motherboard. Preferably, the removable adhesivesurface includes a repositionable adhesive disposed at selectedlocations on the removable adhesive surface to allow for easier removalof the display from the motherboard.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example only, withreference to the accompanying drawings, in which:

FIG. 1 is a front plan view of a handheld computing device, accordingthe invention described herein;

FIG. 2 is a schematic view depicting functional details of the handheldcomputing device;

FIG. 3 is a front plan view of the motherboard of the handheld computingdevice;

FIG. 4 is a rear perspective view of the LCD display of the handheldcomputing device.

FIG. 5 is a perspective view of the resilient layer of the LCD display;

FIG. 6 is a perspective view of the LCD display, fitted with theresilient layer;

FIG. 7 is an exploded view showing the LCD display relative to themotherboard; and

FIG. 8 is a perspective view of the LCD display secured to themotherboard.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, there is shown a handheld computing device,denoted generally as 100, provided according to one aspect of theinvention. The handheld computing device 100 includes a display 122, afunction key 146 and a system motherboard 102 (not shown) disposedwithin a common housing. The display 122 is a self-contained peripheraldevice that is connected to the system motherboard.

The function key 146 functions as a power on/off switch for the handheldcomputing device 100, and may also function as a backlight key for thedisplay 122.

In addition to the display 122 and the function key 146, the handheldcomputing device 100 includes user data input means for inputting datato the data processing means. As shown, preferably the user data inputmeans includes a keyboard 132, a thumbwheel 148 and an escape key 160.

Typically, the handheld computing device 100 is a two-way wirelesscommunication device having at least voice and data communicationcapabilities. Further, preferably the handheld computing device 100 hasthe capability to communicate with other computer systems over theInternet. Depending on the exact functionality provided, the wirelesshandheld computing device 100 may be referred to as a data messagingdevice, a two-way pager, a wireless e-mail device, a cellular telephonewith data messaging capabilities, a wireless Internet appliance, or adata communication device, as examples.

FIG. 2 depicts functional details of the handheld computing device 100.Where the handheld computing device 100 is enabled for two-waycommunication, the motherboard 102 will incorporate a communicationsubsystem 111, including both a receiver 112 and a transmitter 114, aswell as associated components such as one or more, preferably embeddedor internal, antenna elements 116 and 118, local oscillators (LOs) 113,and a processing module such as a digital signal processor (DSP) 120. Aswill be apparent to those skilled in the field of communications, theparticular design of the communication subsystem 111 will be dependentupon the communication network in which the device is intended tooperate. For example, the handheld computing device 100 may include acommunication subsystem 111 designed to operate within the Mobitex™mobile communication system, the DataTAC™ mobile communication system,GPRS network, UMTS network, EDGE network or CDMA network.

Network access requirements will also vary depending upon the type ofnetwork 119. For example, in the Mobitex and DataTAC networks, thehandheld computing device 100 is registered on the network using aunique identification number associated with each handheld computingdevice. In UMTS and GPRS networks, and in some CDMA networks, however,network access is associated with a subscriber or user of the handheldcomputing device 100. A GPRS handheld computing device thereforerequires a subscriber identity module (SIM) card in order to operate ona GPRS network, and a RUIM in order to operate on some CDMA networks.Without a valid SIM/RUIM card, a GPRS/UMTS/CDMA handheld computingdevice may not be fully functional. Local or non-network communicationfunctions, as well as legally required functions (if any) such as “911”emergency calling, may be available, but the handheld computing device100 will be unable to carry out any other functions involvingcommunications over the network. The SIM/RUIM interface 144 is normallysimilar to a card-slot into which a SIM/RUIM card can be inserted andejected like a diskette or PCMCIA card. The SIM/RUIM card can haveapproximately 64K of memory and hold many key configuration 151, andother information 153 such as identification, and subscriber relatedinformation.

When required network registration or activation methods have beencompleted, the handheld computing device 100 may send and receivecommunication signals over the network 119. Signals received by antenna116 through communication network 119 are input to receiver 112, whichmay perform such common receiver functions as signal amplification,frequency down conversion, filtering, channel selection and the like,and in the example system shown in FIG. 2, analog to digital (A/D)conversion. A/D conversion of a received signal allows more complexcommunication functions such as demodulation and decoding to beperformed in the DSP 120. In a similar manner, signals to be transmittedare processed, including modulation and encoding for example, by DSP 120and input to transmitter 114 for digital to analog conversion, frequencyup conversion, filtering, amplification and transmission over thecommunication network 119 via antenna 118. DSP 120 not only processescommunication signals, but also provides for receiver and transmittercontrol. For example, the gains applied to communication signals inreceiver 112 and transmitter 114 may be adaptively controlled throughautomatic gain control algorithms implemented in DSP 120.

The handheld computing device 100 preferably includes a microprocessor138 which controls the overall operation of the device. Communicationfunctions, including at least data and voice communications, areperformed through communication subsystem 111. Microprocessor 138 alsointeracts with further device subsystems such as the display 122, flashmemory 124, random access memory (RAM) 126, auxiliary input/output (I/O)subsystems 128, serial port 130, keyboard 132, speaker 134, microphone136, a short-range communications subsystem 140 and any other devicesubsystems generally designated as 142.

Typically, the communication subsystem 111, flash memory 124, RAM 126,I/O subsystems 128, serial port 130, keyboard 132, speaker 134,microphone 136, microprocessor 138, and the subsystems 140, 142 areprovided on the motherboard 102, and the display 122 is provided as aself-contained unit that is physically mounted, and electricallyconnected, to the motherboard 102. This aspect of the invention will bediscussed in further detail below.

Some of the subsystems shown in FIG. 2 perform communication-relatedfunctions, whereas other subsystems may provide “resident” or on-devicefunctions. Some subsystems, such as keyboard 132 and display 122, forexample, may be used for both communication-related functions, such asentering a text message for transmission over a communication network,and device-resident functions such as a calculator or task list.

The operating system software used by the microprocessor 138 ispreferably stored in a persistent store such as flash memory 124, whichmay instead be a read-only memory (ROM) or similar storage element (notshown). Those skilled in the art will appreciate that the operatingsystem, specific device applications, or parts thereof, may betemporarily loaded into a volatile memory such as RAM 126. Receivedcommunication signals may also be stored in RAM 126.

As shown, the flash memory 124 can be segregated into different areasfor both computer programs 158 and program data storage 150, 152, 154and 156. These different storage areas indicate that each program canallocate a portion of flash memory 124 for their own data storagerequirements. In addition to its operating system functions, preferablythe microprocessor 138 enables execution of software applications on thehandheld computing device. A predetermined set of applications thatcontrol basic operations, will normally be installed on the handheldcomputing device 100 during manufacturing. One set of basic softwareapplications might perform data and/or voice communication functions,for example.

A preferred software application may be a personal information manager(PIM) application having the ability to organize and manage data itemsrelating to the user of the handheld computing device such as, but notlimited to, e-mail, calendar events, voice mails, appointments, and taskitems. Naturally, one or more memory stores would be available on thehandheld computing device to facilitate storage of PIM data items. SuchPIM application would preferably have the ability to send and receivedata items, via the wireless network 119. In a preferred embodiment, thePIM data items are seamlessly integrated, synchronized and updated, viathe wireless network 119, with the user's corresponding data itemsstored or associated with a host computer system.

Further applications may also be loaded onto the handheld computingdevice 100 through the network 119, an auxiliary 110 subsystem 128,serial port 130, short-range communications subsystem 140 or any othersuitable subsystem 142, and installed by a user in the RAM 126 orpreferably a non-volatile store (not shown) for execution by themicroprocessor 138. Such flexibility in application installationincreases the functionality of the device and may provide enhancedon-device functions, communication-related functions, or both. Forexample, secure communication applications may enable electroniccommerce functions and other such financial transactions to be performedusing the handheld computing device 100.

In a data communication mode, a received signal such as a text messageor web page download will be processed by the communication subsystem111 and input to the microprocessor 138, which preferably furtherprocesses the received signal for output to the display 122, oralternatively to an auxiliary I/O device 128. A user of the handheldcomputing device 100 may also compose data items such as email messagesfor example, using the keyboard 132, which is preferably a completealphanumeric keyboard or telephone-type keypad, in conjunction with thedisplay 122 and possibly an auxiliary 110 device 128. Such composeditems may then be transmitted over a communication network through thecommunication subsystem 111.

For voice communications, overall operation of the handheld computingdevice 100 is similar, except that received signals would preferably beoutput to a speaker 134 and signals for transmission would be generatedby a microphone 136. Alternative voice or audio I/O subsystems, such asa voice message recording subsystem, may also be implemented on thehandheld computing device 100. Although voice or audio signal output ispreferably accomplished primarily through the speaker 134, display 122may also be used to provide an indication of the identity of a callingparty, the duration of a voice call, or other voice call relatedinformation for example.

Serial port 130 in FIG. 2, would normally be implemented in a personaldigital assistant (PDA)-type handheld computing device for whichsynchronization with a user's desktop computer (not shown) may bedesirable. The serial port 130 enables a user to set preferences throughan external device or software application and would extend thecapabilities of the handheld computing device 100 by providing forinformation or software downloads to the handheld computing device 100other than through a wireless communication network.

Other communications subsystems 140, such as a short-rangecommunications subsystem, is a further optional component which mayprovide for communication between the handheld computing device 100 anddifferent systems or devices, which need not necessarily be similardevices. For example, the subsystem 140 may include an infrared deviceand associated circuits and components or a Bluetooth™ communicationmodule to provide for communication with similarly enabled systems anddevices.

FIG. 3 depicts the physical structure of the motherboard 102. Asdiscussed above, the communication subsystem 111 (including the receiver112, transmitter 114, and antenna elements 116, 118), flash memory 124,RAM 126, I/O subsystems 128, serial port 130, keyboard 132, speaker 134,microphone 136, microprocessor 138, and the subsystems 140, 142 areprovided on the motherboard 102.

FIG. 4 is a rear perspective view of the display 122. The display 122 isprovided as a self-contained unit that is physically mounted, andelectrically connected, to the motherboard 102. The display 122 includesa display panel 103 (see FIG. 7), and a printed circuit board 104 thatcarries the display electronics. The printed circuit board 104 may beprovided as a rigid, flexible or semi-rigid circuit board. Preferably,the display panel 103 comprises a glass LCD display panel Alternately,however, the display panel 103 may comprise a plastic LCD display panel.

The display panel 103 and the display circuit board 104 are retainedtogether within a cover assembly 105 that secures the display panel 103to the display circuit board 104. Preferably, the cover assembly 105comprises a front metal cover plate, and a rear metal cover plate thatis coupled to the front cover plate. In addition to securing the displaypanel 103 to the display circuit board 104, the front and rear metalcover plates provide ESD protection for the display panel 103 and thedisplay circuit board 104.

The display 122 also includes a resilient layer 106 (see FIG. 7) that isdisposed between the circuit board 104 and the motherboard 102. As shownin FIG. 5, the resilient layer 106 includes an upper horizontal end 123a, a lower horizontal end 123 b, and a pair of vertical sides 125 a, 125b extending between the horizontal ends 123 a, 123 b. The resilientlayer 106 has a first adhesive surface that adheres the resilient layer106 to the circuit board 104, and a second adhesive surface that adheresthe resilient layer 106 to the motherboard 102. Typically, the firstadhesive surface is a permanent adhesive surface, and the secondadhesive surface is a removable adhesive surface, although theproperties of the first and second adhesive surfaces could be reversed.Alternately, however, both the first and second adhesive surfaces couldcomprise removable or permanent adhesive surfaces, if desired.

Preferably, the second adhesive surface comprises a repositionaladhesive that is provided only at selected locations on the secondadhesive surface so as to allow for easier removal of the display 122from the motherboard 102. In particular, as shown in FIG. 6, preferablythe repositional adhesive is disposed along the upper and lowerhorizontal ends 123 of the resilient layer 106, but not along thevertical sides 125. Alternately, the repositional adhesive may bedisposed along the vertical sides 125 of the resilient layer 106, butnot along the upper horizontal end 123. Other configurations for therepositional adhesive will be apparent. For instance, the repositionaladhesive may be disposed at the corners of the resilient layer 106.

Preferably, the resilient layer 106 comprises a slow rebound urethanefoam layer that absorbs shear and impact forces. The resilient layer 106is selected such that when the display 122 is adhered to the motherboard102, and shear and impact forces are applied to the display panel 103,the resilient layer 106 absorbs those forces and thereby limits thelikelihood of the display panel 103 becoming damaged.

In addition to the resilient layer 106, the display 122 also includes abacklight (not shown), and a light guide frame 121 that is disposedbetween the backlight and the display panel 103. The backlight and thelight guide frame 121 are sandwiched between the front and rear coverplates of the cover assembly 105. The front and rear cover platesinclude locking tabs (not shown) that fasten the front and rear metalcover plates to the light guide frame 121. From front to back, thedisplay 122 comprises the front cover plate, the display panel 103, onepair of orthogonal brightness enhancing films, a light diffuser film,the light guide frame 121, the backlight, a light reflective plate, theprinted circuit board 104 and the rear cover plate.

The light guide frame 121 includes two pairs of snap clips 107 a, 107 b,107 c, 107 d that extend towards the motherboard 102, and assist insecuring the display 122 to the motherboard 102 of the handheldcomputing device. 100. The snap clips 107 include laterally-opposed headportions 108 that loosely engage the opposing edges of the motherboard102 so as to allow the display 122 to move towards or away from themotherboard 102, within a limited range as defined by the snap clips107.

Preferably, the light guide frame 121 also includes a pair of pins 109a, 109 b that extend towards the motherboard 102. The pins 109 a, 109 bare received in S correspondingly-located holes 110 a, 110 b that areformed in the motherboard 102, and serve to align the display 122 withthe motherboard 102. The holes 110 are slightly oversized so as to allowthe display 122 to move laterally relative to the motherboard 102,within a limited range as defined by the snap clips 107 and the size ofthe holes 110. Although the light guide frame 121 is shown having twopairs of snap clips 107, and a pair of pins 109, it should be understoodthat the light guide frame 121 may have any number of the clips 107 andthe pins 109, as required by the dimensions and shape of the display122.

The display 122 is mounted to the motherboard 102 by aligning the pins109 a, 109 b with the locate holes 110 on the motherboard 102, and thenpressing the display 122 against the proximate surface of themotherboard 102, so that the second adhesive surface of the resilientlayer 106 adheres to the motherboard 102 At the same time, the snapclips 107 loosely engage the edges of the motherboard 102, with theassociated head portions 108 loosely engaging the opposite surface ofthe motherboard 102.

When the display 122 is mounted to the motherboard 102, the display 122is resiliently mounted to the mother board 102, in that the resilientproperties of the resilient layer 106 allows the display 122 to moveslightly (towards, away, and laterally) relative to the motherboard 102.As a result, if the handheld computing device 100 is struck or dropped,the impact forces applied to the display panel 103 will be less thanprior art computing devices. Accordingly, the likelihood of the displaypanel 103 of sustaining damage from such an impact is reduced.

For a handheld computing device 100 which has a 2.2 inch LCD display 122(with a module thickness of 3.2 mm), favourable drop testcharacteristics (at a drop height up to one metre) can be obtained usinga 0.53 mm resilient layer 106 thickness of Rogers Corporation PORON(trademark) cellular, extra soft, slow rebound PET-supported urethanefoam P/N 4790-92-25021-04. The PET-supported side of the resilient layer106 is coated with a 0.051 mm of 3M 9667, 467WP or 467MPF permanentadhesive, and the other side is selectively coated with 0.063 mm ofAdchem 8311 M-74 low tack removable adhesive. As will be apparent, for alarger LCD display 122 (or a thinner, more fragile LCD display 122), thethickness of the resilient layer 106 would be increased.

A number of factors (such as the size and mass of the display 122 andthe environment in which the handheld computing device 100 will be used)will dictate the characteristics of the resilient layer 106, theadhesives applied to the resilient layer 106. For example, to facilitateease of disassembly (eg. for repair purposes), the surface area overwhich the repositional adhesive is applied to the resilient layer 106should be as small as possible. On the other hand, the surface area overwhich the permanent and repositional adhesives are applied to theresilient layer 106, and the adhesive characteristics of the adhesivesthat are applied to the resilient layer 106, should be selected so thatthe display 122 will not become dislodged from the motherboard 102 whenthe handheld computing device 100 is exposed to impact forces typical ofthose encountered during use of the handheld computing device 100.

To reduce the likelihood of impact damage to the display panel 103,preferably the adhesives are applied symmetrically to the resilientlayer 106, and the resilient layer 106 itself has a symmetrical shape,so as to cause the impact forces to be applied uniformly to the displaypanel 103. Further, since there are no compression forces from the frontcover plate to balance the rear support forces from the rear cover plateat the centre of the display panel 103, preferably the resilient layer106 has a hole cut in its centre to thereby support the display panel103 at its outer edges.

The present invention is defined by the claims appended hereto, with theforegoing description being merely illustrative of a preferredembodiment of the invention. Those of ordinary skill may envisagecertain modifications to the foregoing embodiments which, although notexplicitly discussed herein, do not depart from the scope of theinvention, as defined by the appended claims.

1. A display for a handheld computing device, comprising: a LCD displaypanel; a circuit board carrying display electronics for the displaypanel; a cover assembly securing the display panel to the circuit board;and a resilient layer adhered to the circuit board for securing thedisplay to the computing device.
 2. The display according to claim 1,wherein the display further includes a backlight, and a light guideframe disposed between the backlight and the display panel, the lightguide frame including at least one snap clip for further securing thedisplay to the handheld computing device.
 3. The display according toclaim 2, wherein the resilient layer has a first adhesive surfaceadhered to the circuit board, and a second adhesive surface for adheringthe display to the computing device.
 4. The display according to claim3, wherein one of the adhesive surfaces comprises a repositionaladhesive disposed along selected portions of the one adhesive surface.5. The display according to claim 3, wherein the first adhesive surfacecomprises a permanent adhesive surface, and the second adhesive surfacecomprises a removable adhesive surface.
 6. The display according toclaim 5, wherein the removable adhesive surface comprises a repositionaladhesive disposed along selected portions of the second adhesivesurface.
 7. The display according to claim 2, wherein the cover assemblycomprises a front cover plate and a rear cover plate, the display paneland the circuit board being disposed between the cover plates, the coverplates being fastened to the light guide frame.
 8. The display accordingto claim 2, wherein the resilient layer comprises a urethane foam layer.9. A handheld computing device comprising: a system motherboard; and adisplay resiliently secured to the system motherboard, the displaycomprising: a LCD display panel; a circuit board carrying displayelectronics for the display panel; a cover assembly securing the displaypanel to the circuit board; and a resilient layer add to the circuitboard and the motherboard
 10. The handheld computing device according toclaim 9, wherein the display further includes a backlight, and a lightguide frame disposed between the backlight and the display panel, thelight guide frame including at least one snap clip farther securing thedisplay to the handheld computing device.
 11. The handheld computingdevice according to claim 10, wherein the resilient layer has a firstadhesive surface adhered to the circuit board, and a second adhesivesurface adhered to the motherboard.
 12. The handheld computing deviceaccording to claim 11, wherein one of the adhesive surfaces comprises arepositional adhesive disposed along selected portions of the oneadhesive surface.
 13. The handheld computing device according to claim11, wherein the first adhesive surface comprises a permanent adhesivesurface, and the second adhesive surface comprises a removable adhesivesurface.
 14. The handheld computing device according to claim 13,wherein the removable adhesive surface comprises a repositional adhesivedisposed along selected portions of the second adhesive surface.
 15. Thehandheld computing device according to claim 10, wherein the coverassembly comprises a front cover plate and a rear cover plate, thedisplay panel and the circuit board being disposed between the coverplates, the cover plates being fastened to the light guide frame. 16.The handheld computing device according to claim 10, wherein theresilient layer comprises a urethane foam layer.